This invention relates to power cable joint structures and more particularly to a power cable joint structure including an improved sheath isolation of a cable shielding layer.
In order to decrease the sheath loss caused in the cable shielding layer or a metal sheath of an electric cable, a cross-bonding method is used in a conventional system and an electrical separation portion is formed in the shielding layer in, for instance, each phase of a three-phase circuit. It is necessary that the sheath isolation be designed to withstand not only abnormal surge voltages, but also the induced voltages between the cable conductor and the cable shielding layer. A sheath isolation is formed in an EHV CV cable by winding thin XLPE tapes, the same material as the cable isolation, on the joint, and then by molding the wound tapes to tight insulation.
Since, however, the thin insulating tape is wound in several turns, a disadvantage is incurred in that the longer on-site work is required. Moreover, it is difficult to maintain a uniform thickness of the insulator of the sheath isolation over the entire outer periphery of the cable insulation. The quality of on-site work therefore depends more upon the skill of the field workers.